The invention relates in general to devices which can display an image of a scene and, more particularly, to a method and apparatus for automated detection and indication of movement within an observed scene.
There are existing devices which include a detector that produces successive images of infrared radiation emitted by a scene, and which use this information to present a series of visible images on a display. In certain applications, an operator will observe the display, for the purpose of monitoring activity of persons or objects such as vehicles within the scene. However, it is sometimes difficult for the operator to discern the presence of a person or object of interest within the scene, even when the person or object is moving. For example, where the operator has been observing the display for a fairly long period of time and is experiencing some fatigue, the operator may entirely overlook the presence of a person or object, even if the person or object is moving.
In an attempt to address this problem, pre-existing systems have been developed which attempt to automatically detect and identify movement of a person or object of interest. These systems use techniques that are known in the industry as moving target indicator (MTI) techniques. These MTI systems are intended to automatically detect and flag movement of a person or object within a scene, so that an operator is less likely to miss the person or object. Although these pre-existing MTI systems have been generally adequate for their intended purposes they have not been satisfactory in all respects.
For example, some pre-existing systems simply place a symbol or icon around a region in which movement is believed to have been detected. This leaves the operator with the task of attempting to visually discern the target within the region identified by the symbol or icon. Moreover, the pre-existing design requires the use of a substantial amount of additional hardware and software, including multiple processors, large amounts of memory, and relatively large and complex algorithms. The additional hardware involves a substantial amount of added cost, power, space and/or weight. Consequently, in many existing systems, implementation of these pre-existing MTI techniques is physically impractical and cost prohibitive. This is particularly true of existing systems which are portable and operate from battery power, where size, weight, power consumption and cost are significant design criteria. Still another problem is that, where the determination of whether there has been motion is made in an automated manner, for example by a software algorithm, false alarms can occur.
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus which can efficiently and effectively detect and identify movement within an observed scene. According to the present invention, a method and apparatus are provided to address this need, and involve: responding to radiation from a scene by producing successive images of the scene, each image including a plurality of pixels which each have a respective pixel value representative of a level of radiation corresponding to that pixel; assigning each pixel in each image to one of a first class and a second class when that pixel respectively meets and fails to meet a criteria, the criteria being met when the current pixel value for the pixel differs by at least a threshold amount from a history value which is a function of the pixel value of that pixel in at least one prior image; converting each image to an adjusted image by effecting an adjustment to the pixel values of the pixels in a selected one of the first and second classes; and sequentially displaying the adjusted images.